Photographic element



United States Patent ()fiice 3,316,097 PHOTOGRAPHIC ELEMENT Louis M. Minsk and Edward P. Abel, Rochester, N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Dec. 21, 1964, Ser. No. 420,203 8 Claims. (Cl. 96-114) This invention relates to gelatin-silver halide emulsions, and more particularly to gelatin-silver halide emulsions having increased covering power of developed silver, and to the process for preparing such elements.

The maximum optical density of a silver image of a photographic film after exposure, processing and drying, and hence the covering power, appears to depend not only upon the amount of silver which results from the development process, but also upon the way in which the silver is laid down in the photographic element during processing and the stresses to which it is subjected in the drying step. The term covering power as used herein refers to the ratio of the optical density of developed silver to the actual quantity of silver.

The intimate structure and density of the silver deposit produced by the reduction of silver halide to metallic silver is influenced during processing and drying by the vehicle in which the silver halide grains are suspended. It therefore appears desirable to modify the vehicle in some manner whereby the covering power of developed silver is increased, thereby providing an increase of maximum density, an increase in gamma and very often an increase in speed. It is, of course, desirable that the modification of the vehicle does not interfere with other photographic properties of the emulsion.

It is one object of our invention to provide gelatin photographic emulsions which exhibit an increase in covering power of developed silver. Another object of our invention is to prepare photographic emulsions having an increase in covering power of developed silver, which emulsions are not adversely affected in their other sensitometric characteristics, such as density, resolution and acutance. Other objects of our invention will appear herein.

These and other objects of our invention are accomplished by incorporating in gelatin silver halide emulsions a polymer containing repeating units having the following formula:

FORMULA 1 wherein R is a carbon chain of from 1 to carbon atoms substituted with from 1 to 3 substituents having the formula -COXR R X being selected from the group consisting of R being hydrogen or lower alkyl (1 to 5 carbon atoms); and R and R each are selected from the group consisting of hydrogen, alkyl groups of 1 to 5 carbon atoms, alkoxy substituted alkyl groups of 1 to 5 carbon atoms,

3,3 1 6,097 Patented Apr. 25, 1 967 and hydroxy substituted alkyl groups of from 1 to 5 carbon atoms. In a preferred embodiment of our invention, we incorporate in gelatin silver halide emulsions a polymer containing repeating units having the following formula:

OO O

FORMULA 2 where n is an integer from 1 to 5. We have found that gelatin silver halide emulsions containing polymers having these repeating units exhibit an increase in covering power of developed silver, which results in an increase of maximum density, gamma and very often an increase in speed. We have also found that the sensitometric characteristics of the emulsion are not adversely atfected by the subject polymers.

We have further found that the covering power of developed silver may be increased with copolymers having repeating units as defined by Formulas 1 and 2 above with other monomers, such as vinyl alcohol andother vinyl monomers including those represented by the following formula:

[CHz(llH-] FORMULA 3 wherein Y is a'photographically inert group such as hydroxyl, an ester such as acetoxy, propionyloxy or butyryloxy; an amide including Nalkyl and N,N-dialky1 amides wherein the alkyl groups contain 1 to 5 carbon atoms, such as methyl, ethyl, propyl, butyl or amyl; or a carbamate group such as -OCONH-R -COOR wherein R and R each are carbon chains of 1 to 5 carbon atoms, preferably alkylene.

The polymers and copolymers which may be employed to increase the covering power of developed silver of gelatin silver halide emulsions in accordance with our invention may be prepared in any convenient manner such as by treating the reaction product of poly(vinyl alcohol) and an ester of isocyanato monoor polybasic fatty acid with an amine. The reaction of the isocyanato compound with the poly(vinyl alcohol) may be partial or complete, as may be the reaction of the amine with the initial reaction product. The preparation of the polymers and copolymers employed in accordance with our invention is illustrated in Examples 1-6.

Example I.T he preparation of p0ly(vinyl ,BJzydroxyethylcqrbamyl-methylcarbamate) mole percent reaction) In a 5-liter flask equipped with a stirrer, thermometer, reflux condenser with calcium chloride tube, and a dropping funnel were placed 2160 ml. of pyridine and 264 g. of low-viscosity poly(vinyl alcohol) that had been dried overnight in a 50 C. air oven. The stirred suspension was heated to C. in a Glas Col mantle and 542 g. of ethyl isocyanatoacetate were added dropwise at the rate of approximately 56 drops/second. Within 51'() minutes after the start of the addition, the slurry began to clear and the viscosity increased. As the heating and stirring were continued, the viscous dope usually became gelatinous, yet soft enough to allow some mixing. After minutes, the addition of the ethyl isocyanatoacetate had been completed. The temperature of the reaction mixture was 119 C. Heating was continued for /2 hour with the temperature dropping spontaneously to 110 C. After 802 g. of ethanolamine had been added through the dropping funnel over a /2-hour period, 480 ml. of distilled water were added slowly. The reddish-colored gel began to break apart and in minutes a smooth, homogeneous dope was obtained. Heating and stirring were continued for 4 and /2 hours at 90100 C. The dope was cooled to 60 C. and precipitated by pouring into stirred isopropyl alcohol. The soft-yellowish polymer, after being allowed to soak overnight in fresh isopropyl alcohol, was washed for /2 hour, with decantation after each wash, a total of 7 times. The soft polymer hardened on washing and broke up into small granular pieces. The solid was dissolved in the mill by the addition of 1 and /2 liters of water to obtain a viscous, bright yellow dope of pH 9.40. The dope was treated with a sufiicient quantity of Amberlite IR-120 ion exchange resin to reduce the pH to 2.32.

A sample of this acidic dope was isolated in isopropyl alcohol for analysis. The main portion of the dope was adjusted to a pH of 6.20 with NaOH. The yield was 565 grams dry weight.

Example 2.The preparation of poly(vinyl fl-hydroxyethylcarbamylmethylcarbarrzate) In a 2-liter flask equipped with a stirrer, thermometer, reflux condenser with calcium chloride tube, and a dropping funnel were placed |1080 ml. of pyridine and 3 moles=132 g. of low-viscosity poly(vinyl alcohol) that had been dried overnight in a C. air oven. The stirred suspension was heated to 92 C. in a Glas Col mantle and 2.1 moles (70 mole percent 272 g.) of ethyl isocyanatoacetate were added dropwise over a A- hour period. The temperature of the dope rose to 115 C. Heating was continued for /2 hour while the temperature dropped spontaneously to 107 C. External cooling lowered the temperature to 90 C. and the polymer was isolated by pouring the dope into distilled water. The soft, yellow solid was washed a total of 6 times in a one-quart W.P. mill with fresh changes of distilled Water. A sample of the polymer was redissolved in acetone, reprecipitated in ethyl acetate and dried under vacuum at room temperature. The nitrogen content was found to be 5.9 percent, which indicated that the intermediate contained 73 weight percent of combined vinyl carbethoxymethylcarbamate.

The damp solid, amounting to 500 g., was placed in a 2-liter bottle containing 300 g. of aminoethanol. The bottle was sealed and tumbled for several days at room temperature until a viscous yellow dope was obtained. The polymer was isolated by pouring the dope into stirred ethyl acetate. The soft yellow solid was washed by kneading in several changes of fresh ethyl acetate and then taken up in 500 ml. of distilled water. The aqueous solution of polymer was treated with a sufficient quantity of Amberlite IR-120 ion exchange resin to reduce the pH of the dope to 2.70. A sample of this dope was isolated for analysis by precipitation in ethyl acetate and drying in a vacuum oven at 35-40 C. The nitrogen content was found to be 10.35 percent, equivalent to weight percent of combined vinyl B-hydroxyethylcarbamylmethylcarbamate; the ethoxyl content was 3.0 per cent, equivalent to 11.5 weight percent of combined unreacted vinyl carbethoxymethylcarbamate, and a carboxyl equal to 0.34 ml. N NaOH/g., equivalent to 4.85 weight percent of combined vinyl carboxymethylcarbamate. This leaves 23.65 weight percent of combined vinyl alcohol .in the polymer.

The main portion of the dope was adjusted to a pH of 6.0 with dilute NaOH. The yield was 268 g. dry weight.

Example 3.-The preparation of poly(vinyl fl-lzydroxyethylcarbamylmethylcarbamate) (70 mole percent reaction from butyl isocyanatoacetate) In a 2-liter flask equipped with a stirrer, thermometer, reflux condenser with calcium chloride tube, and a dropping funnel were placed in 720 ml. of pyridine and 88 g. of poly(vinyl alcohol) that had been dried overnight in a 50 C. air oven. The stirred suspension was heated to 93 C. in a Glas Col mantle and 220 g. of butyl isocyanatoacetate were added dropwise. Within 10 minutes the slurry began to clear and the viscosity increased. Shortly thereafter the viscosity decreased and a smooth, homogeneous dope was obtamed. The addition of the butyl isocyanatoacetate required /3 hour. Heating and stirring were continued for 2 hours while the temperature dropped spontaneously from 116 C. to C. A total of 270 g. of ethanolamine was added over a fii-hour period, followed by ml. of distilled water. Heating and stirring were continued for 4% hours at 95-100 C. The dope was cooled to 60 C. and precipitated by pouring into stirred isopropyl alcohol. The soft cake, after soaking overnight in fresh isopropyl alcohol, was washed for /2 hour, with decantation after each wash, a total of 6 times. The polymer hardened on washing and broke up into small granular pieces. The solid was dissolved in the mill by adding 500 ml. of distilled water. The basic dope was treated with a suflicient quantity of Amberlite ion exchange resin (IR 120) to reduce the pH to 1.75. A sample of the dope was isolated by precipitation in isopropyl alcohol for analysis. The main portion of the dope was adjusted to a pH 6.0 with alkali. The yield was 206 g. (dry weight).

Example 4.The preparation of poly(vinyl 1,2-bis[;3-hya'roxyethylcarbamyl] ethylcarbamate) In a one-liter flask equipped with a stirrer, thermometer, reflux condenser with calcium chloride tube, and a dropping funnel were placed ml. of pyridine and 22 g. of low-viscosity poly(vinyl alcohol). The stirred suspension was heated to 99 C. in a Glas Col mantle and 134 g. of diethyl a-isocyanatosuccinate were added dropwise. A clear, dark amber dope was obtained while the temperature rose to 119 C. Heating was continued for 2 hours. The polymer was isolated by pouring the dope into distilled water and washed by kneading in fresh distilled water several times. The damp polymer was placed in a bottle containing 600 ml. of ethanolamine and tumbled at room temperature for several days until a viscous, reddish-colored dope was obtained. The polymer was isolated -by pouring the dope into stirred isopropyl alcohol and washed several times in fresh isopropyl alcohol to remove the major portion of the residual ethanolamine. Two hundred milliliters of distilled water Were added to dissolve the polymer, and the aqueous solution was treated with a suflicient quantity of Amberlite IR-120 ion exchange resin to reduce the pH to 2.60. A sample of this dope was isolated for analysis by precipitation in isopropyl alcohol and drying in a vacuum oven at 35-40 C. The isolated sample was found to contain 11.4 percent nitrogen, equiyalent to 63.5 weight percent of combined vinyl 1,2-(dihydroxyethylcarbamido)ethylcarbamate; 7.5 percent ethoxyl, equivalent to 21.6 weight percent of combined unreacted vinyl 1,2-(dicarbethoxy)ethylcarbamate, and a carboxyl equal to 0.73 ml. N NaOH g., equivalent to 14.7 weight percent of combined vinyl 1,2-(dicarboxy)ethylcarbamate. The main portion of the dope was adjusted to a pH of 6.20 with dilute NaOH using a Beckman Model G pH meter. The yield was 89 g. dry weight.

Example 5.The preparation of poly(vinyl I,3-bis[,8 hydroxyethylcarbamyl]propylcarbamate) (100 mole percent reaction) In a ZOO-ml. flask equipped with a stirrer, thermometer, reflux condenser with calcium chloride tube, and a dropping funnel were placed 72 ml. of pyridine and 8.8 g. of

low-viscosity poly(vinyl alcohol) that had been dried overnight in a 50 C. air oven. The stirred suspension was heated to 90 C. in a Glas Col mantle and 46 g. of

diethyl a-isocyanatoglutarate were added dropwise. The

addition required hour. At this time a smooth, dark amber dope had been obtained and the temperature had reached 113.5 C. Heating was continued for 2 and A hours while the temperature dropped spontaneously to 98 C. The dope was poured slowly into distilled water 6 of the dope was adjusted to pH of 6.10 with dilute NaOH. The yield was 33 g. dry weight.

Examples 7-9 TABLE I Preparation Wt. Percent Calculated from Analyses Reference Alkanol Unreacted Carboxy Vinyl Alcohol R-NCO R-N H2 Amide Ester Carbamate (by Dif- Carbamate Carbarnate ference) Example 7 Ethyl isoeyanatoacetate 2-amino th l-.-. 75. 2 6- 1 18. 7 E m 2 1 do 60. 11.5 4. 85 23.15 Example 8 -do. 80.0 10. 0 4. 0 6. 0

- (1 40. 0 29. 6 3. 34 27. 06 1 42. 0 32.5 3. 04 22. 46 Butyl isoeyanatoacetate. 7 0 Diethyl a-isocyanatoglutarate 44. 7 36. 4 6. 1 12. 8 Diethyl a-isocyanatosuecinatm... .d0 63. 5 21. 6 14. 7 Ethyl isocyanatoacetate Iminodicthanol- 46- 2 28. 0 9. 0 16. 8

to precipitate a soft, light-yellow polymer. After washing the soft cake in water several times, it was dissolved in acetone and reprecipitated -by again pouring into stirred water slowly. The soft cake was washed by kneading in 'distilled water and dried in a vacuum oven at 40-45" C. Forty-six grams of tatfy-like polymer were obtained that analyzed for 5.0/4.9 percent nitrogen and 31.5 percent cthoxyl.

The polymer was placed in a bottle with 300 g. of ethanolamine and 50 ml. of water and tumbled at room temperature for several days until a viscous amber dope was obtained. The polymer was isolated by pouring into stirred acetone and Washed several times in fresh acetone to remove the major portion of the residual ethanolamine. Water was added to dissolve the polymer, and the aqueous solution was treated With a sufficient quantity of Amberlite IR-12O ion exchange resin to reduce the pH to 2.30. A sample of this acidic dope was isolated for analysis. The main portion of the dope was adjusted to a pH of 6.55 with aqueous NaOH. The yield was 28.8 g. dry weight.

The acidified polymer analyzed for the following:

=8.6/8.3; ethoxyl=l2.0; titration=0.28 ml. N NaOH/g. polymer.

Example 6.--Tlze preparation of p0ly(vz'nyl bisLo-hydroxyetlzyl]carbamylmelhylcarbamate) In a SOO-ml. flask were placed 200 ml. of iminodiethanol, ml. of distilled water, and 43 g. of poly(vinyl carbethoxymethylcarbamate) intermediately prepared as in Example 1. The mixture was heated on a steam bath with gentle stirring for approximately 24 hours, during which time a clear, reddish dope had been obtained. The polymer was isolated by pouring the dope into stirred isopropyl alcohol. The soft yellow solid was kneaded by hand several times in fresh isopropyl alcohol and then taken up in 100 ml. of distilled water. The aqueous solution was treated with a sufficient quantity of Amberlite IR-IZO ion exchange resin to reduce the pH to 2.70. A sample of this dope was isolated for analysis by precipitation in isopropyl alcohol and drying in a vacuum oven at 3540 C. The isolated sample was found to contain 8.7 percent nitrogen, equivalent to 46.2 weight percent of combined vinyl bis(,B-hydroxyethyl)carbamylmethylcarbamate; 7.3 percent ethoxyl, equivalent to 28 weight percent of combined unreacted vinyl carbethoxymethylcarbamate, and a carboxyl equal to 0.62 ml. N NaOH/ g. equivalent to 9.0 weight percent of combined vinylcarboxymethylcarbamate. This leaves 17 percent of combined vinyl alcohol in the polymer. The main portion The polymers obtained in Examples 1-9 were tested for their ability to increase the covering power of developed silver by incorporating the polymers in a standard sulfur-gold sensitized high-speed coarse-grain silver bromoiodide emulsion of the type commonly used in medical -ray films. Each emulsion sample was coated on a cellulose acetate support at a coverage of 560 mg. of silver and 900 mg. of gelatin per square foot. A sample of each coating was exposed on an Eastman 1B Sensitometer and processed for 3 minutes in Kodak Developer l9B. The results obtained with the polymers of EX- amples 1, 2, 8, and 9 were sufficiently similar to the results obtained with emulsions containing the polymer contained in Example 7 that the photographic results thereof have not been separately listed. The improvement in increased covering power of developed silver in emulsions in accordance with the invention is demonstrated by the photographic results set out in Table II.

TABLE II Concen- Polymer tration Relative Gamma Fog Dm per Ag Speed mole, g.

Control 100 l. 84 0. 04 1. 70 Example 7 43 123 2. 4O 0. 05 2. 10 Control 100 2. 20 0. 06 l. 86 Example 4 60 123 2. 76 0. 06 2. 30 Example 6 60 123 2. 0. (l6 2. 25 Control- 1.60 O. 05 1. 60 Example 5 60 138 2. 36 0.06 2. 36 Example 3 60 132 2. 06 0.07 2. 10

Example 10 A terpolymer of vinyl alcohol, vinyl carboxymethyl carbamate and vinyl N-butylcarbamylmethylcanbamate containing approximately 24 weight percent vinyl carboxymethylcarbarnate and 32 weight percent vinyl N- butylcarbamylmethylcarbamate was tested for its ability to increase covering power of developed silver as described above. The results are shown in Table III.

7 Examples 11-18 A number of polymers were made in accordance with the method described in Examples 1-6. The principal reactants are described in Table IV, together with a description of the content of the polymers obtained.

8 rived from a poly(vinyl alcohol) of inherent viscosity from 0.10 to 0.90, and preferably from 0.30 to 0.50. The inherent viscosity is measured in water at a concentration of 0.25 g. per 100 ml. of solution at 25 C.

The invention has been described in detail with par- TABLE IV [Additional polymers] Preparation Wt. Percent Example No. lkanol Unreacted Carhoxy Vinyl R-NCO RNH1 Amide Ester Carbamate Alcohol (by Carbamate Carbamate Ditl'erence) 11. Ethyl isocyanatoacetate 95 4.3 0.7 12.s do H 48.1 21.9 18.6 11.4 13 61 29 14. 2-ethoxyethylamine 6 9. 3 34.1 15 2-amino-2-n1ethyl-l-propanel 35 33. 4 13. 6 18 16 2-amino-2-ethyl-l ,3-pr0pauedl0l 64 l 36 17 Q-amino-Z-hydroxy methyl-1,3- 67 7. 0 25. 0

propanediol. 18 .....(10 2-aminoethanol. 52.7 11.1 24.8 11.4

The polymers obtained in Examples 11-18 were incorporated in emulsions and tested as described above. The results obtained show that each of the polymers increased the covering power of developed silver, as described in Table V.

TABLE V Polymer Cone. g./ Rel. Fog 30 Ag mole Speed Example 11 45 126 1. 48 0. 14 o 0 100 1.18 0.14 30 102 1. 68 0. 13

As indicated heretofore, our invention relates both to the use of homopolymers and copolymers containing carbamylated repeating units. The most useful polymers in accordance with the invention contain from 30 to 100, and preferably 50 to 75 percent by weight of repeating units as defined in Formula 1 or 2 above, the remainder of the polymer being composed of repeating units in accordance with Formula 3 above. The most important feature of the polymers of the invention is the substituted *carbamate groups attached to the polymer chain, as described.

The polymers and copolymers of our invention are incorporated in gelatin silver halide emulsions at a ratio of about 10 to 75 grams per mole of silver and from 5 to 50 percent by weight of the gelatin employed in the emulsion.

Particularly useful results are obtained when the poly- .rners of the invention are incorporated in X-ray emulsions, which may be used, for example, in X-ray elements of the type having integral intensifying screens, such as those described in Kennard et al. US. patent application Serial No. 223,377, filed September 13, 1962, now abandoned in favor of continuation applications Serial Nos. 364,244 and 364,245, both filed May 1, 1964.

The gelatin silver halide emulsions of our invention may contain various chemical sensitizers, stabilizers, speed-increasing compounds, coating aids, and gelatin hardeners and plasticizers, such as those described in US. Patent 3,039,873.

The molecular weight of the polymers which we ernploy in our invention may vary over a wide range; the most useful molecular weights are such as would be deticular reference to preferred embodiments thereof but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. A gelatin silver halide photographic emulsion having good covering power of developed silver containing about 5 to 50%, based on the weight of the gelatin, of a polymer containing repeating units having the following formula:

CNH-R1 wherein R is a carbon chain of from 1 to 5 carbon atoms, substituted with from 1 to 3 substituents having the formula COXR R X being selected from the group consisting of R being selected from the group consisting of hydrogen and alkyl groups of 1 to 5 carbon atoms; and R and R each are selected from the group consisting of hydrogen;

alkyl groups of 1 to 5 carbon atoms; alkoxy substituted alkyl groups having 1 to 5 carbon atoms; and hydroxy substituted alkyl groups of from 1 to 5 carbon atoms.

2. A gelatin silver halide photographic emulsion having good covering power of developed silver containing about 5 to 50%, based on the weight of the gelatin, of a polymer in which at least 30% by weight of the repeating units are represented by the following formula:

wherein R is a carbon chain of from 1 to 5 carbon atoms substituted with from 1 to 3 substituents having the formula -COXR R X being selected from the group consisting of R being selected from the group consisting of hydrogen and alkyl groups of 1 to 5 carbon atoms; and R and R each are selected from the group consisting of hydrogen; alkyl groups of 1 to 5 carbon atoms; alkoxy substituted alkyl groups having 1 to 5 carbon atoms; and hydroxy substituted alkyl groups of from 1 to 5 carbon atoms, and 0 to 70 per-cent of repeating units having the following formula:

[-CHP? H-] wherein Y is a photographically inert group.

5. A photographic support having coated thereon an emulsion as described in claim 1.

6. A gelatin silver halide photographic emulsion having incorporated therein a vinyl polymer containing combined hydroxyalkyl carbamylalkylcarbamate groups attached to the polymer chain in a concentration suflicient to effectively increase the covering power of developed silver.

7. A gelatin silver halide photographic emulsion having incorporated therein a vinyl polymer containing combined alkylcarbamylalkylcarbamate groups attached to the polymer chain in a concentration sufficient to eifectively increase the covering power of developed silver.

8. A gelatin silver halide photographic emulsion having incorporated therein a vinyl polymer containing combined alkoxyalkylcarbamylalkylcarbama-te groups attached to the polymer chain in a concentration sufiicient to effectively increase the covering power of developed silver.

No references cited.

NORMAN G. TORCHIN, Primary Examiner. R. H. SMITH, Assistant Examiner. 

1. A GELATIN SILVER HALIDE PHOTOGRAPHIC EMULSION HAVING GOOD COVERING POWER OF DEVELOPED SILVER CONTAINING ABOUT 5 TO 50%, BASED ON THE WEIGHT OF THE GELATIN, OF A POLYMER CONTAINING REPEATING UNITS HAVING THE FOLLOWING FORMULA: 